Any one of the many allegations levelled at Silvio Berlusconi over the years would probably be sufficient to sink a prime minister in most countries, but the scandal which could finally undo him is perhaps the most scurrilous of them all. It combines an underage belly dancer, ribald sex parties and claims of political interference with the police.

The unwitting protagonist in this particular tale is Karima el-Mahroug, who also goes under the stage monicker of Ruby Rubacuori, or Ruby Heartstealer.

According to a series of media reports last October, Berlusconi met Mahroug, then 17, through Nicole Minetti, a TV showgirl turned dental hygienist who acquired a post in Berlusconi's Freedom People party after catching his eye while cleaning his teeth.

Mahroug insisted that she had not slept with the 74-year-old prime minister, but she told Italian newspapers that she attended "bunga bunga" sex parties at his mansion near Milan. At one of these, Mahroug said, she sat next to Berlusconi, who later took her upstairs and gave her an envelope containing €7,000. She said he also gave her jewellery.

Their acquaintance came to light after Mahroug was arrested in Milan for allegedly stealing cash. The station commander said that she was released after police received a call from the prime minister's office saying – incorrectly – that she was the granddaughter of Egypt's long-serving president, Hosni Mubarak.

Berlusconi ridiculed opposition calls for him to resign over the affair, saying: "As always, I work without interruption and if occasionally I happen to look a beautiful girl in the face, it's better to like beautiful girls than to be gay."

• Berlusconi is accused of bribing his lawyer, David Mills – the estranged husband of the British MP and former cabinet minister, Tessa Jowell – to give false testimony. Mills was convicted in 2009 of taking a $600,000 bribe from Berlusconi in return for perjuring himself in two trials in the 1990s, involving tax and the affairs of his media empire. Italy's highest appeals court quashed Mills's conviction, but later made it plain it had done so because of a technicality and not because it believed him to be innocent.

• In another case, dating back to 2003, Berlusconi is accused of tax fraud and false accounting over deals made by the Italian broadcaster Mediaset relating to the acquisition of US film rights. The case centres around deals made in 1994 and 1995 in which Mediaset channelled the rights through offshore companies and allegedly inflated the price of these rights declared to Italian tax authorities.

• Berlusconi is under investigation by magistrates for allegedly putting pressure on Italy's media watchdog to block a TV talk show which discussed the supposed mafia links of a member of his government. A wiretap of a phone call reportedly reveals Berlusconi urging Giancarlo Innocenzi, a senior member of the parliament-appointed body, to "shut down" the show, Annozero, on the state RAI network. Transcripts have the prime minister saying: "It's obscene. Now you need to make a concerted effort to push RAI to say enough, we're shutting everything down."

Separately, the prime minister has endured years of claims connected to his self-professed fondness for the company of attractive women who are a fraction of his age, some of whom were subsequently put forward for government roles or his party list for European elections. Perhaps the best known of this group was Mara Carfagna, a former model and showgirl who became an MP for Berlusconi's party, then Forza Italia, before being made equal opportunities minister in 2008.

A throwaway comment about Carfagna in 2007 – "I'd marry her if I weren't married already" – was perhaps the root cause of Berlusconi's recent woes. Berlusconi's wife, Veronica Lario, was so unimpressed she wrote a public letter calling his behaviour "damaging to my dignity". Then, in April 2009, Lario said she was filing for divorce, condemning her husband's "consorts with minors" after he attended the 18th birthday party of an aspiring model, Noemi Letizia.

In the following months a series of increasingly lurid stories emerged about the prime minister's alleged associations with younger women, a number of whom were said to be working as prostitutes.

The first details about the alleged "bunga bunga" sex parties at Berlusconi's houses came from Patrizia D'Addario, who worked as an escort. She secretly recorded suggestive phone calls with the prime minister and talked of up to 20 young women attending a single party. She later alleged she had slept with the prime minister and that he knew she was an escort.

Around the same time, long-lens photographs appeared in a Spanish newspaper showing Berlusconi at his Sardinian villa with a group of young women, some topless, and a naked man in what appeared to be a state of sexual arousal, later identified as the former Czech prime minister, Mirek Topolanek.

However, the most serious claims followed the revelations about Mahroug. One of the most damaging came from Nadia Macri, a 27-year-old ex-prostitute who told prosecutors she twice supplied Berlusconi with sexual services and flew to his Sardinian villa with 25 or 30 other young women and a consignment of marijuana.

Next came claims that he spent as much as €400,000 in state funds to fly a 32-year-old Bulgarian actor and director, Michelle Bonev, described as a "personal friend", to the Venice film festival.

A week later Berlusconi narrowly survived a no confidence vote in Italy's upper house of parliament, but for many observers the question was now when, not if, the flood of sleazy accusations would force him from office